These guys have actually applied a bit of thought to it:
Do Consumer Drones Endanger the National Airspace? Evidence from Wildlife Strike Data | Mercatus
They haven't made unfounded statements like:
Most of these <2kg devices are quadcopter or hexcopter devices which (unlike birds) are not very aerodynamically shaped. (Ever noticed how the majority of birds are deflected over or under an aircraft by the boundary layer)?
Really, the aerodynamic shape of a bird is what deflects them?
Another gem:
...fitted with GPS that has a "come home" capability if data link is lost. However, if GPS signal is lost (or GPS is not enabled / fitted) the device (which may well have started below 400ft more than 3NM from an aerodrome) will continue on its last vector (possibly climbing and possibly towards an aerodrome) until it runs out of battery. Then they become a real 2 kg brick.
Have you actually ever set up a return to home feature on a drone? Even if you set it up to climb to 400 feet upon losing signal or low battery, you would have to be very damn close to the threshold for it to become an issue for landing aircraft. Consider an aircraft on profile is at 320 feet AGL 1nm from the aim point, which for many aircraft is 300m in from the threshold. You'd basically have to have turned on your drone and launch initially right on the aerodrome boundary for it to be a threat.
I am quite sure that when the word gets out that the < 2kg commercial sector is unregulated, the quantity of these devices in use will expand exponentially with their potential uses limited only by imagination.
As mentioned previously, market forces will stop this from happening. There simply isn't enough work for drones to "fill the skies" doing sub 2kg commercial work. It won't take long for guys to see there is little return on investment for buying a $2000 Phantom (plus other expenses), then charging $30 a photoshoot.
The threat is the idiots who fly them recreationally to high levels. The rule changes will not stop these guys. However, consider that the new rules might actually improve safety as they should define a minimum distance from an aerodrome. Do you realise the way CASR part 101 is written means anyone can buy a Phantom off the net and fly right next to an airport, as long as they are below 400 feet and not in the departure and approach path? Heck, could fly one right up to Brisbane Tower if I wanted to.
Have a read through CASR 101 - doesn't mention a blank 3nm restriction anywhere. The CASRs say "not above 400 feet with 3nm of an aerodrome". The brochures and posters CASA put out say 'should not' fly within 3nm, but there actually isn't any law prohibiting it at the moment as long as you stay below 400 feet. The real restriction is on UOC holders - the conditions listing on their certificate will prohibit them within 3nm (no matter the height) unless certain conditions are met.